THREATS, THREATS AND MORE THREATS ALTHOUGH SENT TO ME IN ERROR

I have tried since October to sort out the Telkom bill. Telkom have reiterated that it is in error. I have sent Nudebt all the documentation needed as proof which they asked for, called and called and called. Sometimes call is answered, but then put through to another dpt who do not answer. I have emailed numerous times but get absolutely no acknowledgement even though Outlook shows that it was delivered and read. Now for the 3rd month in a row I get a threatening email. I don't know which way to turn any longer. Could someone help me please.